Assemblies and methods for unwinding and feeding of packaging film into a form, fill and seal packaging machine are known in the art. A number of other machines that process web material similar to film, such as printing presses, employ similar feeding assemblies and methods. These feeding assemblies typically include means for supporting and unwinding a supply web roll and means for feeding the web into the processing machine.
In the case of a form, fill and seal packaging machine, the film is ultimately formed into an open package, filled with a product, and sealed to retain the product until opened for use. A wide variety of products, most notably food items, are packaged in this manner. To further explain, the basic combination of a form, fill and seal packaging machine is disclosed in U.S. Pat. No. 4,727,707, assigned to the assignee of the present invention. It discloses a method and assembly for controlling the feed of packaging film from a supply roll over a former, where the film is formed into an open tube. A filling means provides a measured amount of product into the bottom of the tube where a package or bag is being formed. The package is then sealed across the top to yield a filled, hermetically sealed package with the product on the inside (see FIGS. 2-4). The '707 patent actually covers a particular improved control routine for film registration utilizing registration marks detected by a photoelectric cell and triggering the various form, fill and seal operations.
It is desirable to minimize the down-time of the packaging machine so that a maximum number of packages or bags can be produced during each unit time. This necessarily means that not only is a reliable high speed package forming, filling and sealing operation required, but also a reliable high speed film feeding/registration arrangement is a necessity, as illustrated in the '707 patent.
In prior art assemblies, film is typically supplied for feeding along the feed path into a form, fill and seal portion of the machine by loading or installing a roll of the film on a spindle or web roll cradle, and controllably rotating the roll to unwind the film. A significant disadvantage of these prior art packaging film unwinding arrangements is the lost operating time caused during change-over when a roll of film is exhausted and a new roll must be loaded and brought on stream. This change-over typically requires an operator to stop the packaging machine to load a new roll of film on the spindle or cradle, thread the film along the feed path and then restart and regulate the machine operation. Typically, lost machine production time is between 10-30 minutes.
The potential lost operation time can be further magnified because a single operator is, in many instances, required to keep several machines operating simultaneously. Thus, if two or more machines require a new roll to be loaded at about the same time, or an emergency occupies the operator's attention at a time when a new roll of film is required, the interruption and lost operating time are detrimentally increased.
Some prior art feeding assemblies and methods have sought to correct or alleviate this problem by incorporating dual roll supporting and unwinding equipment so that upon exhaustion or expiration of an active roll, the threading of the film from a standby roll can begin immediately. This reduces the roll change-over interruptions because the operator can have the standby roll pre-loaded in the machine. Thus, the overall down-time of the packaging machine is reduced.
Some web feeding approaches for other types of machines have suggested going a step farther to include a provision for automatically splicing the tail-end of the web of the active roll to the head-end of the web of the standby roll so that the web is truly continuously fed without any roll change-over interruption.
In these web feeding assemblies and methods, it is highly desirable to include provision for implementing the splicing by a control means upon detection of the tail-end of the web of the active roll being at a splice position along the feed path. In addition, upon expiration of the active roll of the web and its release from the spindle, there must be provisions for maintaining tension on the web. This is necessary to maintain tracking of the web through the machine and to ensure that the tail-end is properly oriented to be spliced upon reaching the splice position.
When successful, this splicing operation alleviates much of the problem of a single operator trying to keep several machines operating simultaneously. It can result in minimizing, and indeed, eliminating roll loading and change over interruptions. The operator has a much wider window of time within which to load new rolls on the machines without risking interruption and lost operating time. In theory, an operator merely installs a new roll onto the standby spindle at any time during unwinding of the active roll prior to its expiration, and the machine can continue operating indefinitely without interruption.
However, prior art methods and assemblies for feeding webs supplied on rolls into processing machines including such splicing provisions possess significant drawbacks and disadvantages. For instance, the arrangements that I am aware of employ moving mechanical parts to mechanically move the head-end and tail-end of the webs into splicing engagement. Adhesive means typically located between the head-end and tail-end are designed to hold them together once the webs are forced together. These moving mechanical parts typically are opposing plungers or plates that forcefully slap the head-end/tail-end together upon detection in real time of the head-end and tail-end being present between them.
Moving mechanical parts utilized to mechanically slap the head-end/tail-end of webs together in this manner are subject to inordinate wear and tear. Heavy maintenance and continuous adjustment to account for the wear that occurs are commonplace complaints of the operators. Furthermore, this brute force approach tends to cause the web to burst if a slight error in synchronization of the operation is experienced.
It is also known that slapping the head-end/tail-end of the webs together with adhesive located between them is particularly problematic when the adhesive is applied in liquid or paste form. Particularly when applied in excessive amounts, the adhesive can squeeze out due to the excessive force of the slap action, resulting in it tending to clog around the moving mechanical parts, and eventually impede or jam their operation.
Another drawback of prior art web feeding assemblies and methods is the lack of convenient operator accessibility to load the head-end of the web of the standby roll into the splice ready position. Specifically, prior to expiration of the active roll, the operator loads the head-end into a holding means in the splice ready position where it is maintained awaiting the tail-end of the web of the active roll. Typically the web of the active roll is in close proximity to the holding means, and manual intervention can cause inadvertent interference and damage to the feeding of the web of the active roll. Shut-down of the processing machine results.
Another problem associated with prior art feeding assemblies and methods that include splicing provisions is the subsequent processing and handling of the head-end/tail-end splice section. That is, the splice section must be retained along the feed path throughout the entire processing machine to maintain the continuous web until the final cut-off point in the process. It is desirable to track the splice section through the entire machine, to inhibit further processing of it, and to recognize it at the cut-off point and dispose of it. Prior assemblies and methods have not addressed the problems of tracking the splice section through the machine to inhibit its processing, and/or to remove it after cut-off.
U.S. Pat. No. 4,455,190 to Bianchetto et al. discloses an apparatus and method for splicing two webs together so that the web is substantially continuously fed into a processing machine. In this case the processing machine is a printing press (see column 1, lines 14-15). The webs are fed from two rolls and spliced together at a splicing station (see FIG. 1). This prior art apparatus utilizes vacuum means for holding the head-end of the web of the standby roll at the splicing station. The web of the active roll as it is expiring causes actuation of a pneumatic cylinder and, correspondingly, downward movement by the plate thereby slapping the two films together. The objective is for both webs to adhere to the adhesive strip between them, effecting a splice (see FIGS. 4D-4G).
This '190 patent also includes a suggestion for retracting the holding means to facilitate loading of the head-end of the web of the new roll so as to be positioned spaced from the splicing station (see FIGS. 4A-4C). However, no mounting details are provided and an operator must move several other components out of the way to permit the movement.
U.S. Pat. No. 4,880,178 to Goulette also discloses an arrangement for splicing the head-end of web of a standby roll to the tail-end of the web of an active roll so that continuous or semi-continuous feeding is effected. The control bar moves downwardly (FIGS. 10 and 11), causing the webs to be slapped together with a tape in between to thereby implement a splice.
Similarly, U.S. Pat. No. 4,722,489 to Wommer discloses a device for splicing the web head-end of a standby roll to the web tail-end of an active roll (see FIG. 1). Again, moving plates 3 must slap the head-end/tail-end together (see FIG. 4) to effect a splice.
Thus, all of these prior art assemblies and methods for splicing two webs together include mechanical moving parts subject to great wear and tear and a tendency to stress, and possibly burst the web just from normal operation. As a result, the parts tend to require regular maintenance at short intervals and continuous adjustment, and occasional shut-down of the machine is required to manually splice a broken web, and rethread the web. In addition, none of the references teach a device or method for tracking the splice section through the machine so that further processing of the splice section can be inhibited, and thus efficiently discarded. Inhibiting the processing of the splice section is referred to as operating the machine in a "dry cycle mode."
Thus, despite these prior art attempts, the continuous feeding of a web, and particularly relatively thin flexible packaging film for use in a form, fill and seal packaging operation, by splicing the film of the rolls together, remains a difficult, and generally problematic procedure. Specifically, (1) the presence of moving mechanical parts to slap the webs together; (2) the lack of a simple means for retracting the head-end holding means to facilitate loading of the new standby roll; and (3) the lack of any provision for efficiently tracking the splice section through the machine and inhibiting its further processing, are particularly identified.